At church we have a combination of computer and audio gear which I am loosely responsible for maintaining, and I’ve written about some of this before. A couple of years ago we rationalised the racks by the computer and as part of this I put in a rack-mounted switch. I was on a budget so ended buying as new from ebay a ‘Dynamode SW240010-R‘.
This was inexpensive (which is why I bought it) and ‘as new’ from ebay. I was a bit wary of it because I wasn’t familiar with the brand but it looked OK and worked fine when installed.
However, a couple of weeks ago it became clear that the network wasn’t working, and one glance at the switch showed that it had failed. The main power light was flashing on and off weakly and none of the individal port lights were working. There wasn’t much time to consider a fix as it was important to get it going, so we bought a new one (TP Link this time). However I wanted to see if the Dynamode could be reapired. From recent experience, I have found that a lot of these failures are due to power supply problems – and specifically capacitors. Particularly in cheap equipment like this the capacitors are of poor quality and deform when they get warm over time. The actual solid state stuff is pretty robust these days and much less likely to fail. The voltages from the power supply wander all over the place and this causes very strange behaviour.
Opening up the unit as expected there was a small power supply board and quite a lot of fresh air:
What was immediately obvious was that one of the capacitors was obviously bulging (circled in red above). It is a 10V 2200uF part, as is the other one on the right hand side. I removed the board, desoldered and replaced both of the capacitors, plugged it back in and held my breath…
Success! The switch now lights up properly and works fine again. Very pleasing to be able to get it going again. It is now surplus to requirements for church so will either keep as a spare or sell on. I am confident now that the replacement capacitors are much better quality than those I removed so hopefully the fault should not recur.